\begin{table}%ta2
%%\centering

\par
\caption{\label{comp}Comparison stars.}
\begin{tabular}{c c c c} 
\hline  \hline\noalign{\smallskip}
Number\tablefootmark{a} & $V$ [mag] & $R$ [mag] & $I$ [mag] \\
\hline
1    & 15.79 & 14.68 & 13.81 \\
2    & 14.86 & 13.95 & 13.18 \\
3    & 14.43 & 13.33 & 12.27 \\
4    & 13.72 & 12.61 & 11.66 \\
5    & 11.84 & 11.05 & 10.43 \\
6    & 15.30 & 14.12 & 13.19 \\
\hline 
\end{tabular}
\tablefoot{\tablefoottext{a}{The numbers correspond to the labels in Fig.~\ref{compfig}}.}  
\end{table}